Supraventricular tachycardia (SVT) is a series of rapid heartbeats that begin in or involve the upper chambers (atria) of the heart. SVT can cause the heart to beat very rapidly or erratically. As a result, the heart may beat inefficiently, and the body may receive an inadequate blood supply. In controlled studies in the United States, bolus doses of 3, 6, 9, and 12 mg of adenosine were studied to determine the effectiveness of the medication on converting SVT to normal sinus rhythm. A cumulative 60% of patients with SVT converted to normal sinus rhythm within one minute after an intravenous bolus dose of 6 mg adenosine, and a cumulative 92% converted after a bolus dose of 12 mg of adenosine. Adenosine slows conduction time through the A-V node, can interrupt the reentry pathways through the A-V node, and can restore normal sinus rhythm in patients with SVT, including SVT associated with Wolff-Parkinson-White Syndrome. Intravenously administered adenosine is rapidly cleared from the circulation via cellular uptake, primarily by erythrocytes and vascular endothelial cells. Adenosine has a half-life of less than 10 seconds in whole blood.
Adenosine injections are generally given as a rapid bolus via a peripheral I.V. route. The bolus dose is then generally followed with a rapid saline flush to facilitate urging the adenosine towards the patient's heart before degrading due to the short half-life. The recommended doses for adults are 6 mg given as a rapid I.V. bolus, administered over a 1-2 second period, followed by a 12 mg bolus dose of adenosine if the first dose does not result in elimination of the SVT in 1-2 minutes. The 12 mg dose can be repeated a second time if required. The recommended neonatal dose is 0.05-0.1 mg/kg, followed by increased doses in 0.05-0.1 mg/kg increments every 1-2 minutes until termination of the SVT. In adults, the bolus adenosine dose is generally followed with a 20 ml saline flush and, for neonatal applications, the dose is generally followed by a 5-10 ml saline flush.
Current systems for delivering first the adenosine dose and then the saline flush include the use of two syringes connected to a T-connector or stopcock. A stopcock is attached to a capped I.V. line with an adenosine syringe on one port and a saline syringe (e.g., 10 ml) on a second open port. The adenosine is then administered over 1-2 seconds, the stopcock is adjusted to access the second syringe, and the saline flush is then delivered to the patient. Such systems can have limitations because of the time needed to transition the T-connector or stopcock from the first syringe to the second syringe. Because the half-life of adenosine is so rapid (i.e., less than 10 seconds), even small amounts of time lost can make a significant difference whether the patient is able to return to a normal sinus rhythm. There are also frequent user errors associated with the stopcock or T-connector systems. If the wrong syringe is initially depressed, the full amount is not administered from one or both syringes, the stopcock is not fully adjusted to transition to the second syringe, or a variety of other issues occur, the consequences for the patient can be severe. The current system also involves a relatively large number of steps to set up and deliver, where improved time efficiency and reduced steps may be advantageous.
Adenosine is described by way of example, where numerous other medications and biologics, such as epinephrine, are delivered in a similar manner. Such other medications frequently have a short-half life, can result in life-threatening consequences if administered improperly, and/or can be inoperative if improperly administered.